TM-5-5420-279-10
FRACTURE CONTROL PLAN
Sect/
Contents
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Para
FRACTURE CONTROL IN FIELD ...................................................................................A-1
INSPECTION AND ACTION REQUIREMENTS..............................................................A-3
A.1.1.1
The regions of the bridge have been divided into five zones A to E as shown in
A.1.1.2
Zone A involves the bottom chords and regions with welded attachments at the
bottom of the side skin. This is the most critical, as tolerance for cracks in these
regions are extremely small.
A.1.1.3
Zone B covers the top chords and trackway deck. Cracks are more likely to affect
serviceability of the bridge, and repair will be a viable option provided any cracks are
found at an early stage.
A.1.1.4
Zone C covers the ends of the panels. Attention should be focused in particular on
the jaws and jaw pinning holes.
A.1.1.5
Zones D and E cover the middle of the side skins and diaphragms respectively.
Inspections can be limited to checking for external damage.
A.1.1.6
The fracture control plan (Table A. 1) has been drawn up to detail the inspection and
any resulting action to be carried out on the bridge panels.
A.1.1.7
This system includes the use of CRACK FIRST fatigue-monitoring gauges. See
so that a crack will start from a known point. As the panel is trafficked, the crack will
grow in length until the coupon finally fails. Once failed the bridge module must be
taken out of service. The fatigue monitoring gauges are only fitted to the Parallel
Modules.
A.1.1.8
The gauge is designed to give an initial warning that the end of the design fatigue life
is being approached. This is indicated by the crack extending between the two
12mm holes. When the crack extends completely from top to bottom of the gauge
then the design life has been reached and the panel must be taken out of service.
The bridge panel should also be removed from service when one of the conditions
listed in the Action Column in Table A. 1 is identified.
